There is known a method to fabricate parts by die forging (cf., SU, A, 570445) residing in that a workpiece is conveyed to a press tool to be die-stamped, clamped by grips engaging with part fins at opposite sides relative to a die impression, removed from the press tool, and transferred for subsequent machining.
However, one disadvantage of the method is that the fins tend to flow arbitrarily through the perimeter of the workpiece, whereas grips are positioned at ends of the workpiece. This in turn results in insufficient quantity of metal extruded toward the grips. Fins are therefore rather thin tending to break during workpiece transfer and leading to an excess of rejects. This prior art method is impossible to use in multistation dies.
The above disadvantages are obviated in a method of die forging (cf., SU, A, 923693) which involves positioning grips at axially opposite workpiece ends to stamp workpiece ends so that part of the metal is caused to flow to the grips and engage therewith. Then the workpiece is raised and transferred by the grips to successive stamping positions. However, workpiece metal tends to flow uniformly to all sides including the central portion resulting in deflection of the workpiece. This deflection affects accuracy of workpiece positioning at successive stations of the press tool which leads to rejection because the central part of the workpiece may fail to rest over the preferred press position. Uniform spread of metal to all sides when stamping end workpiece portions leads to insufficient quantity of metal entering the grips, whereby the grips can fail to reliably hold and transfer the workpiece. At successive press stations the engagement point of the workpiece with the grips can also be deflected, as the midportion of the workpiece is not subjected to stamping and its thickness is greater than the thickness of the workpiece ends, whereas the workpiece is positioned according to the stamped ends, and the grips are lowered for the midportion to bear on the die impression.
The aforedescribed method is materialized in an apparatus (cf., SU, A, 923693) comprising a die, a punch engageable with the die, and grips at either side of the die having the form of endless chains and capable of vertical and horizontal displacement. However, the apparatus features all inherent disadvantages of the prior art method.